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' v man Fon Looms med .my 2s, 194s e santa-sheet s filial nvenbors 'motor F. Sepmch. Maxence RMvono Patented Oct. 5, 1948 LTOFF FOR LOOMS Victor F. Sepavlch and Clarence R. Kronoff, Worcester, Mass., assignors to Crompton & Knowles Loom Works, Worcester, Mass., a corporation of Massachusetts Application July 26, 1946, Serial No. 686,294

This invention relates to improvements in let-y off mechanisms for looms and it is the general object of the invention to provide an electric motor connected to the letoi mechanism and operating under control of warp tension to turn the warp beam.

When heavy beams of large diameters are used the force required to turn the beam, if transmitted solely through the warp threads, would be high enough to create excessive tension in the warp. It is an important object of our present invention to provide a motorv operatively connected' to the beam in such manner as to turn the latter when the warp has attained a given desired maximum tension insuiicient of itself to cause turning of the beam. The operating circuit for the motor is controlled by a Contact responsive to increase in Warp tension as determined preferably froma small group of warp threads ,and preferably independent of the whip L roll which is preferably though not necessarily stationary.

We have found that heavy warp beams are subject to an axial' twist if the driving. means causing rotation of the beam is located at one side only of the beam. It' is another object of our invention to connect the aforesaid motor to the two ends of the beam by means of equalizing mechanism, such as a diiferential, and locate the latter intermediate the ends of the beam vso that equal forces are applied to each end of the beam.

When rotation of large warp beams is controlled by gearing part of which is fastened directly to the beam there is sufficient sag when the beam is full to change the axis of the gear on the beam with respect to the gear with which it meshes, resulting `in breakage of gear teeth. In order to overcome this defect it is another object of our invention to provide chainsfor driving the warp beam through sprocket wheels fastened to the beam. Such a connection be-r tween the beam and its driving mechanism is not damaged by sagging of the beam.

We preferably wrap the chains around the forward parts of the sprocket wheels so that the beam can be readily removed from the loom by a backward motion without requiring disconnection of the chains from their guiding and driving sprockets. Since the chains are interconnected through the diierential mechanism they can be moved independently of each other to t the sprocket wheels secured to the ends of the beam.y

The motor by which the Warp beam is rotated is o claims. (ci. 139-110) f under `control of electronic means including a signal circuit controlled by a warp tension contactor operatively connected to a small group of warp threads. When the warp is under a tension less than the maximum desired tension the contactor is idle and the signal or grid circuit is in a preventive condition which keeps the motor power circuit dead. As soon as the Warp attains the maximum tension desired, however, the contactor closes a contact and alters the signal circuit, making it permissive and allowing the electronic power circuits to turn the motor in a direction to cause the beam to deliver warp for `the weaving operation. The signal circuit vcan be operated by a very feeble current at the contactor and there is therefore no risk of fire.

It isl still another object of our invention to provide manually controlled electric switches connected to the electronic circuits in such manner that the motor can be caused -to turn the beam when the loom is at rest, even though the warp tension contacter be open. This manual control feature is utilized to effect both forward and reverse motions of the motor. After a pickout is madethe motor is reversed to move the fell of the cloth rearwardly to the position which it should occupy for correct resumption of Weaving. The tension contacter controls the reversing circuit and automatically opens it as soon as the desired maximum tension is reestablished in the warp.

Although the takeup exerts a continuous forward pull on the warp the latter is subjected to anv additional forwardly directed force by the reed at each beatup of the lay. The beatup temporarily increases the warp tension above the normal or maximum desired tension, and is likely to close the tension controlled contacter even though the tension be correct both before and after the beatup. In order to prevent the motor from responding to the momentary increase in tension at beatup it is another object of our invention to open the signal circuit at each beatup ter-force.

our invention, but we have found it useful with certain types 4of warp.

When 4the warp beam is full and of large diameter the pull of the Warp by the takeup is at a 3 relatively large distance from the beam axis and has considerable effect in turning the beam. When the beam is nearly empty, however, the warp pull is near the beam axis and has much less turning effect. Under the first condition when the torque is large the beam turns at a slow rate to supply the needed warp, due to its diameter, but under the latter condition the turning is not only much faster, but the torque is much reduced. It is another object of our invention to set the friction -to exert a counter torque less than the forward torque of the takeup when the beam is full, but more than the forward torque when the beam is nearly empty. The motor is connected to the letoif `gearing by a worm which supplements the friction when thev beam is full by acting as a movable stop. the friction and worm jointly opposing the takeup. As the forward torque diminishes a time comes when it can be balanced by the frlctional counter torque, and the worm ceases to act as a stop. Thereafter, as the forward torque continues to diminish it is supplemented by the motor which assists it to overcome the frictional counter torque.

The aforesaid friction mechanism and motor constitute two instrumentalities which jointly op-V pose the takeup to establish the desired maximum warp tension under normal loom operation, and under these conditions the motor itself is not required to supply enough force to create this desired tension. When the warp is to be reversed after a pickout, however, the motor is required to establish the maximum desired tension and should under these conditions be released from the load which the friction mechanism would impose on the motor. It is another object of our invention to provide means by which the friction mechanism is temporarily disabled to have no effect on loading the motor when the latter is reversed to establish the desired maximum warp tension.

With these and other objects in view which will appear as the description'of our invention proceeds, our invention resides in the combination and arrangement of parts hereinafter described and set forth.

In the accompanying drawings. wherein a convenient embodiment of our invention is set forth,

Fig. 1 is a plan view of the letoi! mechanism of a loom made according to our present invention, Dart of the warp being broken away to show the housing for the diil'erential gearing and friction devices,

Fig. 2 is a vertical section on line 2-2 of Fig. 1,

Fig. 3 is an enlarged side elevation partly in section of certain parts shown in Fig. 2,

Fig. 4 is a vertical section on line 4-4 of Fig. 3,

Figs. 5 and 6 are detailed vertical sections on lines 5 5 and 6 6, respectively, of Fig. 4,

Fig. 7 is a horizontal section on line 'I-l of Fig. 4,

Fig. 8 is a vertical section on line l-l of Fig. "I, parts being broken away,

Fig. 9 is a diagrammatic view showing the elec- 'tric control circuits,

Fig. 10 is an enlarged side elevation looking in the direction of-arrow il, Fig. 1, parts being in section,

Fig. 11 is an enlarged plan view of the contactor controller looking in the direction of arrow ii, Fig. 10,

Fig. 12 is a vertical longitudinal section on line i2-i2, Fig. 11,

Fig. 13 is a vertical transverse section on line i3-i3, Fig. 11, and

close or cross the warp when the lay is on front Fig. 14 is a diagrammatic side elevation of a type of loom to which our invention can be applied.

Referring more particularly to Figs. 1, 2 and 14, we have shown a loom frame Il, top and bottom shafts i i and i2, respectively, and harness mechanism i3 for the warp W. The latter is wound on a beam I 4 having end gudgeons Ii rotatable in rearwardly opening cap bearings li carried by brackets ilextendingrearwardlyfromtbelon frame. A stationary whip roll il is mounted on rearwardly extending arms I l also secured to the loom frame. The whip roll may turn on its stationary axis and is located above the beam as shown in Fig. 2.

Referring to Fig. 14, the warp W extends forwardly from the harness frames I3 through the reed 20 of a reciprocating lay 2| and then to the fell 22 of the cloth 2l. The latter passes partly around a takeup roll 2| which may be driven in a forward direction by a train of mechanism 2l including a worm 26 on a horizontal shaft Il. The latter is driven by bevel gear mechanisms 2l operatively connected to the bottom shaft I2. During loom operation the worm turns and advances the takeup roll so that the latter tends to pull the cloth and warp forwardly and continuously, preferably at a uniform rate. The reed beats up toward the cloth each pick of the loom and in doing so subjects the warp to a temporary increase in tension. The harness frames open the warp when the lay is on back center position and center.

The matter thus far described is of usual construction and of itself forms no part of our invention.

Referring more particularly to Fig. 1, the right and left Budseons il of the beam i4 have secured thereto sprocket wheels 3l and 3|, respectively, meshing with chains I2 and Il. The upper part of each chain, as shown more particularly in Fig. 2, is trained around front and back sprockets 34 and Ii, respectively. the latter rotating on a stationarystudltonabracketllsecin'edtothe loom frame. Each of the forward Sprockets 3| is fast with respect to a gear 38 rotatable with its sprocket on a stud Il on the bracket l1.

Ihe right hand gear Il. see Figs. 1 and 2, meshes with a pinion 4I secured to a shaft Il the right end of which turns in a bearing l2, see Fig. 1, formed as part of the bracket 31 at the right side of the loom. In similar manner, the left hand gear Il. see Fig. 1. meshes with a pinion 4I securedtoashaftl turninginabe'aringllon the bracket 31 at the left side of the loom. The shafts extend toward each other but are separate, as will be set forth more particularly hereinafter.

The lower part of each chain extends around a guide sprocket Il rotatable on bearing arm ll extending rearwardly from the loom frame. Each chain is wrapped partly around the front part of its sprocket wheel Il or li. The cap bearings Il are behind the chains and open rearwardlyto permit backward movement of gudgeons il and wheels 3l and Il away from their chains when the beam is removed from the loom.

From the matter thus far described it will be understood that when the shafts Il and ll turn the chains l2 and 33 will cooperate with their respective sprocket wheels on the warp beam to turn the latter. 'I'he mechanism by which rotation of the shafts Il and I6 is controlled is shown more particularly in Figs. 2 to 8. A letoif motor M described more particularly hereinafter is mounted on a stand 50 on the loom frame and has a shaft |v extending rearwardly into a gearreduction unit 52 mounted on' a 4stationary part of the loom, such as a bracket 53, and including a frame 54 shown in section in Fig. 4.

Unit 52 includes a worm 55 secured to and turning with shaft 5| and meshing with a worm gear 5'6 pinned to a shaft 51 rotata le in the unit, see Figs. 3 and 4. Worm 55 is held against substantial longitudinal movement by the frame 54 for a reason which will appear hereinafter. A pinion 58 secured to shaft 51 meshes with a gear 59 pinned to a sh-aft 60. As shown more particularly in Fig. 7, shaft 60 -turns in stationary bearings 6|- and has mountedithereon for free rotation right and left pinion-gear unit-s 62 and 63, respectively. Unit 62 has a pinion 64 integral with a gear 65, while unit '63 has -a similar pinion '66 integral with a gear 61. Bearings 6| are formed on the sides 68 of a stationary casing or housing 69.

A planetary gear case or assembly extends around shaft 60 and has right and left side plates or rings 1| and 12, respectively, see Fig. 7, secured at 13 to a ange 14 integral with shaft 60. Two pairs of planet pinions extend between and are rotatably supported by the side plates 1| and 12, one pair comprising pinions 15 and 1-6, and the other pair comprising pinions 11 and 18. The pinions of each pair mesh with each other, see Fig-8, one pinion of each pair meshing with the gear 65 and the other pinion of e-ach pair meshing with the gear 61. While the pinion-gear units y62 and -63 are free Ato rotate on the shaft 60, they are interconnected by reason of the pairs of planet pinions and gears 65 and 61, and rotation of one of the units 62--63 in one direction will cause rotation of the other unit in lthe opposite direction if shaft 60 is stationary.

v Pinion 64 meshes with a ring gear 80 mounted on a spider 8| keyed as at 82 to the left end of shaft 4|, see Fig. 4. In similar manner, pinion 66 meshes with a ring gear 83 secured to a yspider 84 splined as at 85 to the right end of shaft 4-6. Right and left ball bearings 86 and 81, respectively, are .provided for the spiders 8| and 84, respectively, and are supported in their corresponding side plates 68 of casng`69.

Friction mechanisms IF and iF', shown more particularly in Figs. 4 and 5, are associated with the ring gears 80 and 83, respectively, and each of these mechanisms has disks turning with the ring gears between other disks which will ordinarily be held against rotation. Thus, the left ring gear 83 of mechanism F' has slots or notches 90 which receive lugs 9| on friction disks '92, the lugs vand not-ches requiring the disks 92 to turn with the ring gear 83. Other normally stationary disks 93 have lugs 94 entering notches 95 in a holding member '96 supported by the adjacent reduced ends of shafts 4| and 46, see Fig. 4. Friction mechanism F is similar 'to the mechanism F' and a detailed description of it is not thought necessary. End plates 91 and -98 for the mechanisms F and F', respectively, abut stop shoulders 99 on the holding member 96.

Referring more particularly to Figs. l and 4, shaft 46 is surrounded by a sleeve |05 located between an adjusting nut |06 threaded von the shaft 46 and a vrelatively heavy compression spring |01 the right end of which as viewed in Fig. 4 presses against a collar |08 loosely surrounding the shaft 46. This coll-ar bears against the lef-t side of the ball bearing 81 which in turn is so constructed as -to transmit a force to the right as-viewed in Fig. 4 against the left hand spider 84. The ball bearing 86 at the right of the mechanism, see Fig. 4, is of the end thrust type and is limited as .to movement thereof to .the right by a danse |09 on the right hand side plate 68 of casing 69.

The spring |01 exerts a force to the right against spider 84 and. holds the disks 92 and 93 of friction unitF' in close engagement with each other, and by means of end plate 98, member 96, and end plate 91, forces .the disks of the friction unit F aga'inst'each other and toward the spider 8|. The bali bearing 88 and flange |09 act as stops to limit motion of spider 8| 'to the right. Fig. 4. By varying the location of 'the adjusting nut |06 it is possible to vary the force exerted by the spring |01 against the friction mechanisms F and F'. The holding member 96 floats -on the shafts 4| and 46 and equalizes the frictional forces resisting turning of them.

The holding member 96 is provided with a set of ratchet teeth H0, see Fig. 5, which cooperate with a; hold pawl .pivoted as at ||2 to the stationary casing 69 and tending to remain in the normal position 'shown in Fig. 5 due to gravity to prevent right hand turning of the member'9`6, Fig. 3, by forces transmitted through the friction disks during normal weaving. If a pickout operation is necessary involving backward movement of the warp beam and reversal of shafts 4| and 46 the ratchet i0 can slip under the pawl by a left hand rotation as Viewed inFig. 5.

The previously mentioned warp tension controlled contactor is shown more particularly in Figs. 10 to 13. The loom to which 'the invention is applied includes a stationary center brace H5 supporting acarrier lI |6 for the warp stop motion I|1. Extending rearwardly from the carrier H6 is an arm ||8 to which an upright H9 is secured. The latter has a table |20 extend- 'ing lengthwise of the warp and to which are secured laterally extending front and back stationary guide-s |2| and |22 -under the warp and on which part of the latter rests.

'I'he rear part of the table |20 is formed with a head |25 to which right and left side plates |26 and |21,A respectively, are attached as at |28. see Fig. 13. These side' plates support a switch housing or casing |30 made of insulating material and held in -position on the plates by a bolt |3| and a thumb nut |32. The body has vertical side slots |33 and |34, respectively, which receive the side plates |26 and |21 and assist the bolt |3,|` to hold the casing |30 in fixed position. The casing |30 can be adjusted vertically by means of the bolt and `vertical sl-ot arrangement designated generally at |35.

A lever |36 has a yoked arm |31 pinned or otherwise secured toy a rock shaft |38 mounted for angular movement on the casing |30. A tension cross bar |39 is secured at |40 to arm |31 and rests on a group of warp threads which extendbetween the guides |2| and |22. 'A short arm |4| is secured to the rock shaft |38 and bears against a spring plunger |42 urgedftoward arm |4| by a spring |43 in the casing |30. An adjusting screw |44 is provided to vary Ithe pressure which spring |43 exerts on arm |4I. By varying the setting of the screw |44 rocking of lever |36 in a clockwise direction as viewed in Fig. 12 can be regulated.A The lever |36 can rock around i'ts axis and Ais urged to move down under the action of spring |43 to the fullline position shown in Fig. 12 when the warp is slack, but is raised to the dotted line position when the 7 warp tensionincreases to a desired maximum. A rear arm |66 of lever |66 is secured to rock shaft |36 and has a lateral stud |61 coated with insulating material.

The casing |66 has a cavity |66 containing arm |46 and also three resilient contacts 0r switch blades designated at |66, ISI and |62. These contacts are positioned by insulated bushings |63 held tightly in position by screws |66. and also by insulating washers |66. When the warp is relatively slack, full line position of Pig. 12, and the insulating stud |61 is in high position. the intermediate spring contact |6| will be up against contact |56. When the warp tension increases, dotted line position of Fig. 12, the stud |41 is lowered and moves the intermediate contact |5| away from top contact |66 and into engagement with bottom contact |62.

The three contacts are connected electrically to side electric current conducting springs, see Fig. 13, connected in turn to the electric circuit shown in Fig. 9. Side plate |21 is recessed to receflve right and left spring contacts |66 and 16|, respectively, which engage stationary contact buttons |62 and I 66, respectively, fixed to casing |36. Spring contacts |66 and |6| are insulated from each' other and side plate |21 and are held in place by screw |26. Buttons |62 and |66 are connected by wires |66 and |66 to the top and bottom spring contacts |66 and |62, respectively. The right side plate |26 is recessed to receive a single resilient spring contact |66 engaging a button |61 electrically connected to the intermediate spring contact III by wire |66. Contact |66 is mounted and insulated in a manner similar to that described for contacts |66 and |6|.

Those parts of the warp contactar shown in Figs. l to 13 which respond to variations in warp tension and thus control the spring contacts |66, and |52 are part of the prent invention. but certain details ol' the contactor are not claimed herein, since they are the subject matter of a separate application Serial No. 686.292 filed July 26, 1946 by one of us and another, now Patent No. 2,440,958. Even though these details are not claimed by us. they are shown to complete the description.

The electric circuits and electric controlling devices for the letoff already described are shown diagrammatically in Fig. 9. We use a direct current shunt wound motor M, a full wave rectier to supply direct currentA for theV ileld of the motor M, and also various electronic grid or signal circuits controlled by the warp tension contact controller and controllingy two power tubes which supply direct current for the armature of the motor. We also provide a gang switch normally in neutral or center position but movable manually from that position to either of two other positions to control the letoii.' motor to turn the beam either forwardly or backwardly.

Power for operating the circuits is derived from lines L and L' supplying alternating current. Transformer TR for the rectifying unit RU has its primary |15 connected to lines L and L' by wires |16 and |11, respectively. The secondary of transformer TR has a double power winding |16 and a low voltage winding |16. Full wave rectifier RU comprises a double diode gas ililed electronic power tube 66 having plates |6| and |62 connected respectively to the right and left ends of the double winding |16. The cath'odes or filaments |63 and |66 corresponding to the plates |6| and |62 are kept incandescent by the low voltage winding |16.

The held |66 of the letoil' motor l( is kept energizedbydirectcun'entiiowingintbefollowing ileld circuit whenever wires L and L' are alive: Plates |6| and |62, one at a. time, tube |66, cathodes |66 and |66, one at a time. wire |66 in the filament circuit, wire |61, resistance |66. wire |66, field |66, wire |66, andcentertap |6| of winding |16. mined by theresistance |66, which may if desiredbemadevariableforthemrpose,andtbe fleldremainsconstantiyexcitedsolongaswirca L and L' are alive.

A second transformer TA supplying current for the armature MA of motor l( has its primary |66 connectedtothepowerlinesLandLbywires |66 and |66. This transformer TA also has a double secondary winding |66 with a center tap |61, and a low voltage winding |66. tronic power tubes 266 and 26| have plates 262 and 266 connected one to each end of the double winding |66. The cathodes or filaments 266 and 266 are in a cathode circuit including wire |62 and are kept incandescent by the low voltage winding |66 whenever wires L and L' are alive. A wire 266 leads from center tap |61 and another wire 261 is connected to wire |62 and the cathodea 266 and 266. When lines L and L' are alive wires 266 and 261 are capable of supplying unidirectional current.

A third transformer IG for grids 266 and 266 of tubes 266 and 26| respectively has its primary 2|6 connected to wiresL and L' by the following phase displacing circuit: Wires L and 2li, primary 2|6. resistance R, and wires 2|2 and L'. The secondary 2|6 of transformer TG has a center tap 2|6 and two windings 2|6 and 2|6'which' supply power at a relatively low voltage, such for instance as seven volts, for grids 266 and 266. Therightendofwindingulisconnectedbynesistance R' and wire 2|1 to the grid 266 of tube 26|, and in similar manner the left end of winding2l6isconnectedbyresistanceR2 andwire2|6 to the grid 266. The resistances R and R' protect the tubes 266 and 26| and may be of the order of 40,000 ohms. and phase displacing resistance E may be of the order of 8500 ohms when the lines Land L' supply power at 110 volts at 60 cycles. A small condenser C' of approximately 0.5 microfarad connects wire 261 to wire 2|6 leading from center tap 2|6.

The lower right hand part of Pig. 9 shows a gang switch GS having an assemblage of switches and contacts which in actual practice are located in a box or housing not shown mounted for instance on the front arch of the loom and readily accessible to the weaver. The dexibie contact blades of switch GB tend vto assume tbe neutral4 or central position shown in full lines, and return to that position after being moved manually to either side of the central position. The switch blades are attached to an insulated cross bar 226 movable by a handle 226. As contemplated in the form of the invention which we illustrate herein, the field of the motor is not under control oi the gang switch GS, and its polarity always remains the same regardless of the position of switch GS.

Switch GS has a top blade 266 and its forward and reverse contacts 26| and 262, respectively, an intermediate blade 223 and its forward and reverse contacts 266 and 266. respectively. and a bottom blade 226 and its forward and reverse contacts 261 and 266, respectively. The loan is provided with three switches, B', S2 and BIwhich areinthefullllnepositionshowninll'igJwhen Thestrengthcftneaeldnnieter- Two gas lllled elecl the loom is in operation and in the dotted line positions when the loom is stopped. These three switches S', S2 andvSS can be controlled 'in any convenient manner not shown, as by the shipper handle of the loom.

When the loom is running the motor M operates intermittently and always turns in such a dlrection as to advance the warp beam to deliver warp forwardly for the weaving process. During loom operation the armature is connected to the following automatic forward armature circuit: Wire 201, switch S2, wires 240 and 24|, inductance H to choke back high frequency waves, up through the armature, wires 242 and 243, and switch S3 to wire 206. The blades 232 and 23B are out of engagement with their respective contacts under these conditions so that wires connected to wires 24| and 242 and leading to the switch GS will not be in closed circuits and the armature circuit just traced will be the only circuit completed through the switches S2 and S3. Because ofv the secondary winding |96 current will tend to flow in this armature circuit but will normally be prevented from doing so due to the fact that grids 208 and 209 are negative with respect to their cathodes and prevent flow of current through their respective tubes,

The grids 208 and 209 are under control of the warp tension contactor shown in Fig. 12. When the loom is running and the warp tension is less than the desired maximum tension contacts |5| and |52 will be separated, and the motor M will be' temporarily at rest because of the electric condition of the grids as determined by the following automatic preventive grid circuit: Wire |89, wire 245, resistance R3, wire 246, junction 241, wire 248, high resistance R4, wire 249, resistance R5, and wire 250 to wire |90. Under these conditions the resistances R3, R4 and R5 will be so related that the junction 241 and the grids electrically connected to it through wire 2|9 will be at a low enough potential, or suicientlynegative with respect to the cathodes 204 and 205, to prevent flow of current through the tubes 200 and 20|, and the mounder control of the warp tension and causing the beam to deliver warp as it is used up in the weaving process. A resistance R6 of approximately 10,000 ohms bridges the wires 245 and 250 and is in parallel with a condenser C which may have a capacity of approximately 20 microfarads. resistance R6 and divides the latter into upper and lower parts for a purpose to be described.

The switch LS in wire 24B is closed at all times during the pick or cycle of the loom except when the lay beats up, at which time the switch is opened either by the lay or some loompart moving in time with the-lay. The purpose of switch LS is to prevent the momentary increase in warp tension incident to beatup from shortcircuiting resistance R4. While switch LS is desirable under many conditions, we find that itis not essen-` tial to all applications of our invention. In Fig.

tor will consequently be at rest. Resistances R3,

R4 and R5 may have values, for instance, of 120,000; 1,000,000 and 250,000 ohms, respectively. When the tension of the warp increases to the ldesired maximum contact |5| will be moved down into engagement with contact |52 and the following automatic `permissive grid circuit will be closed: Wires |89 and 245, resistance R3,

wires 246 and 248, lay controlled switch LS in wire 248 (described'hereinafter), contacts |5| and |52, wire 25|, button 252, switch S', wire 249, resistance R5, and wire 250 to wire |90.

This permissive circuit short-circuits the high resistance R4 and resistances R3 and R5 alone determine the potential of the Junction 241. These last two resistances are so related that they raise the potential of junction 241 and grids 208 and 209, or at least make the grids sufilciently less negative with respect to the cathodes to permit current to flow through the tubes 200 and 20| and the armature circuit, and the motor thereupon turns forwardly to supply warp with an attendant reduction in warp tension resulting in upward movement of contact |5| away from contact |52. Resistance R4 is thereupon again put in series with resistances R3 and R5 and the automatic preventive grid circuit is reestablished to stop the motor. This running and non-running condition of the motor continues during loom operation; the motor being that there is a considerable diiference between 14 switch IS is shown closed in full lines, a condition existing when lay 2| is rearward of its beat-up position. When the lay moves to its front center or beat-up position, shown in dotted lines, Fig. ,14, it-pushes switch LS forwardly to the open position shown in dotted lines,

The foregoing preventive and permissive grid contacts derive their potential from the windings of secondary 2|3 of transformer TG. This secondary is isolated and the grids would float electrically, so to speak, without reference to the cathodes 204 and 205 unless connected to the latter in some manner. This connection is afforded by wire 256 which connects the sliding contact 255 to the wire |92 of the cathode circuit. The voltage of junction 241 shifts throughout a range from a minimum to a maximum thereof when resistance R4 is shortcircuited, but the amount by which the upper part of this range exceeds the voltage of the cathodes 204 and 205 will depend upon. the zero level of the preventive grid circuit with respect to the zero level of the cathode circuit. The sliding contact 255 permits a relative raising or lowering of the zero levels of the grid and cathode circuits, and therefore affords a means for controlling the amount of current which can pass through the tubes 200 and 20| and armature MA.

If the cloth being woven is relatively coarse so that only`20 picks of filling are laid to the inch there will be a relatively fast feed of warp and the motor will need to turn relatively fast whenever called into action. Under these conditions the contact 255 will be set to produce a relatively small dierence between the zero levels of the grid and cathode circuits, thereby causing the grids to go to a high value relatively to the cathodes whenever the resistance R4 is shortcircuited. If, on the other hand, a much nner cloth is being woven requiring, for instance picks to the inch, the warp beam' will turn much less for each pick of the loom and the motor must operate at a correspondingly reduced speed. This condition will be brought about by moving the contact 255 so the zero levels ofthe grid and cathode circuits, causing the grids to permit passage of lesscurrent through the tubes 200 and 20| when the resistance R4 is shortcircuited than in the previous instance.

A sliding contact 255 is provided for the the lines L and L' through the previously describedaphase displacing circuit and the phase of the grids will be displaced with respect to the phase oi the plates due to the phase displacement of secondary winding 2|3 with respect to the phase of lines L and L. This phase displacement will ordinarily remain fixed.so long as resistance R is unchanged, but can be altered by a change in the value of resistance R.

It will therefore be seen that the grids are under three controls, the first of which is due to the shift from preventive to permissive and back to preventive grid circuit conditions, the second of which is due to the difference in electric level or zero values of the grid and cathode circuits as determined by contact 255, and the third of which is due to the phase displacement caused by resistance R. Ordinarily the amount of shift in the potential of the junction 241 will not be subject to change, but the difference in zero levels of the grid and cathode circuits can be changed at contact 255 as already suggested.

The operation already described with reference to Fig. 9 is on the assumption that the loom is running and that changing conditions in the warptension cause the motor M to run and stop al- The foregoing description oi Fig. 9 relates to conditions when the loom is operating. It is desirable however to exercise certain controls over the letoi! when the loom is at rest and these lead to additional conditions.y

Under the fourth condition, when the loom has stopped, the control circuits should be inoperative provided switch GS is in its central position. As soon as the loom stops the switches S', S2 and S3 will be moved as already described from their full line to their dotted line positions shown in Fig. 9. Wires 206 and 201 therefore do not have direct connection with the armature except as such connection could be established through switch GS, Under this fourth condition, however, the three blades of switch GS are out of ternately, and on the further assumption that the handle 226 of gang switch GS is in its center or neutral position. This operation of the apparatus may be considered as a first condition, but other conditions are provided for in the circuits shown in Fig. 9.

A second condition would grow out of the accidental movement of switch GS to forward position the effect of which would be to connect the blades 230, 233 and 236 with their upper or forward contacts. While this condition might occur only infrequently it is desirable that if it should occur no interference would result in the normal operations of the armature and grid circuits during loom operation. The only way in which the aforesaid accidental movement of switch GS might affect normal operation when the loom is running would be to create the conditions of a permissive grid circuit. It will be noted, how-I engagement with their contacts and no circuit can be completed from the wires 206 and 201 to the armature. It is also noted under this fourth condition that when switch S moves to its dotted line position it disconnects contact |52 from the grid circuit and the preventive grid circuit is completed through the high resistance R4.

A fifth condition may grow out of desirability to advance 'the warp when the loom is stopped. To effect this condition the handle 226 will be raised the effect of which is to create the following manual fori/ard permissive grid circuit: wire 245, resistance R3, wires 248 and 248, switch LS, wire 210, contact 23|, blade 230, Wire 26|, button l 260, switch S', (now in the dotted line), wire 243,

ever, that contact |52, wire 25| and button 252 are disconnected from button 260 of switch S' when the loom is running, This latter button is conn'ected by wire 26| to the top blade 230 and it is therefore impossible for the latter to have any shortcircuiting effect on the resistance R4 so long as switch S' is in the running full line position. It will thus be seen that the second condition is amply guarded against and cannot alter normal operations.

A third conditionwould be that growing out of accidental lowering of handle 226 during loom operation so that blades 233 and 236 would engage their bottom reverse contacts. Here again, the button 260 would be disconnected from contact |52 and shortcircuiting of resistance R4 would be impossible.

The matter thus far described with respect to the second and third conditions has dealt primarily with the top blade 230, but it will be apparent from Fig. 9 that engagement of blades 233 and 236 with their respective contacts will cause no interference With the normal circuit operations during loom running due to the fact that the rst of these blades is connected by wire 265 to button 266 which is out of contact with switch S2 during loom operation, and likewise the second blade 236 is connected by Wire 261 to button 268 which is out of contact with switch S3 during loom operation.

resistance R5 and wire 250. This circuit shortcircuits the high resistance R4 so that electric conditions at the junction 241 and the grids are such as to permit flow of current through tubes 260 and 20|. The following manual forward armature circuit thereupon becomes operative: wire 201, switch S2, (in the dotted line position), button 266, -wire 265, blade 233, contact 234, wires 21| and 24|, choke coil H, up through the armature. wires 242 and 212, forward contact 231, blade 236, wire 261, button 268, and switch S3, (in the dotted line position), to wire 206. 'I'he motor therefore runs in a forward direction under manual control and will continue so to run as long as the handle 226 is held in raised position.

The sixth and last condition is that in which it may be desired to reverse the beam under manual control. Ordinarily this last condition will exist when the warp is slack and should be pulled back to reestablish the desired maximum tension. The intermediate contact |5| will therefore be up and in contact with contact |50. Lowering the handle 226 to move switch GS will close the following manual reverse permissive grid circuit: Wire 245, resistance R3, wires 246 and 246, switch LS, contacts |5| and |50, wire 215, contact 232, 'blade 230, :wire 26|, button 260, switch S', (in the dotted line position), wire i243, and resistance R5 to wire 250. This last traced circuit shortcircuits resistance R4 and current can flow through the tubes 200 and 20|. The following manual reverse armature circuit thereupon becomes operative: wire 201, switch S2, (in the dotted line position), button 266, Wire 265, 235, wires 212 and 242, down through the armature, coil H, wires 24| and 216, contact 238, blade 236, wire 261, button 263, and switch S3, (in the dotted line position), to Wire 206.

This last traced reverse armature circuit depends of coursefor its operation upon the shortcircuiting of resistance R4, but it will be understood that as the beam is turned backwardly by the motor warp tension increases and eventually when the maximum desired warp tension is atblade 233, contact l tained intermediate contact |51 will 'move down away from contact |50, thereupon opening the in which they interact when weaving from a full to an empty warp beam and a more detailed description of this relationship will now be given.

When the warp beam is full it requires a minimum of angular movement to deliver the warp required 'for a pick of the loom, but when the beam is almost empty a larger angular movement is required. The takeup roll 24 exerts a forward pull on the warp and is the part of the loom which is responsible for the forward feed of the warp threads and their tension. When the beam diameter is large takeup roll 24 exerts a maximum torque on the beam due to the diameter of the latter, but when the beam diameter is .small the takeup torque is greatly reduced.

Throughout the weaving operation in which the beam diminishes from a maximum diameter it is necessary to be able to preserve a desired maximum tension in the warp above which the warp tension will not rise.

The friction mechanisms F and F retard movement of the beam and therefore exert on it a countertorque opposed to the forward torque of the takeup. The motor mechanism. particularly the worm 55 acts at times as a stop for the letotf mechanism, and when acting in this capacity the motor driving mechanism for the beam supplies an additional countertorque resisting forward movement of the Warp by the talreup.v When the motor turns forwardly worm 55 advancesv and this not only turns the Ibeam but has the effect of advancing the stop for the beam.

We s et the friction mechanisms F and F' so that their countertorque which resists turning of the beam lies intermediate the maximum takeup torque when the beam is full and the minimum takeup torque when the beam is nearly empty. Under the first of these conditions the takeup is able to overpower the countertorque of the friction mechanism and it is at this 'time that the worm 55 of the motor acts as a stop to counterbalance the excess of the takeup forward torque over the frictional countertorque until the desired maxi- -mum tension is attained. The motor then turns the Worm to advance the worm thread and temporarily relieves the c'ountertorque of the motor, whereupon the takeup is able to overcome the friction and the warp is advanced to permit a slight drop in the warp tension below the maximum desired tension.

As weaving continues the diameter of the beam diminishes and a time comes when the counterj tertorque of mechanisms F and F'. From this stage in the weaving operation on until the beam is empty the .worm 55 ceases to act as a stop and serves only to turn the beam against the friction.

It is desirable that the friction be able to exert a countertorque which would develop a tension in thev warp above the aforesaid desired maximum, although this is not essential in all applica.-`

tions which can be made of our invention. The resistance to turning of the warp beam due to the manner of vits drive can be relied upon to cori-z tribute a countertorque :which will permit attainment of the, maximum desired warp tension. We lave found in some applications of our invention that the frictional countertorque can be comparatively small, or omitted by release of spring l (81 and full reliance placed on themotor drive to develop countertorque. The advantage of the friction mechanisms F and F' grows out of the :fact that they permit thc use of a smaller motor than would be necessary without them under certain weaving conditions. Whenever used as described the friction mechanism serves as a protector for the motor and its worm, absorbing as it does some of the forward torque of the takeup which would otherwise be transmitted directly tothe worm 55.

During normal loom running the armature of the moto;- is never required to establish the desired maximum tension, since that tension is developed in part by the worm. When the loom is reversed, however, the armature MA is required to establish the maximum desired tension and it should at this time be relieved of any 1aed which the friction mechanisms could impose upon it. The rachet lill and pawl III are provided for this purpose and enable the motor to run reversely without being required to overcome the frictionai resistance of mechanisms F and F1.

From the foregoing it will be seen that we have provided a letoff mechanism operated by a normally idle motor which is called into action by a contractor independent of the whip roll whenever the warp tension attains a. desired maximum. It will furtherbe seen that we have provided` differential mechanism between the motor 'and the beam to turn the ends of the latter by substantially equal forces. Also. the beam turns about a stationary axis but is driven by chains which are not materially affected by any sagging of the beam when the latter is full of warp. The chains engage the iront of their respective beam sprockets and for this reason the beam can be removed from the loom by a backward motion without disturbing theehains. Furthermore, the normally idle motor is controlled by electronic crcuts the operating parts of which are normally Y dead but are energized to cause mot-or turning when the desired maximum warp tension is at- 'tain ed. The manual lswitches permit operation of the letoff either forwardly or reversely when the loom is stopped, and when running backwardly the motor is automatically stopped as soon as the desired maximum warp tension is attained. 'The manual switches permit operation of the letoii' either forwardly or reversely when the loom is stopped. and when runnin:Y backwarr'lv the motor is automatically stopped as soon as the desired maximum warp tension is attained. The loom switches S'. S2 and S3 provide means for altering the electric circuit upon loom stopnage sn 'fhet the. manual switch is able to control the motor M. The lay operates to open the grid circuit at front center and therefore prevents operation of the motor when the warp tension is temporarily increased at beatup. This feature is desirable in some instances but has been found unnecessary when weaving light-weight or loosely woven fabric. The motor and its worm 55 supplement the friction mechanisms to overcome the forward torque of the takeup when the beam diameter is large, but supplement the takeup to overcome the counterforce of friction mechanisms F and F when the beam diameter is small. Under the first of these conditions the worm not only turns the beam but also serves as a stop, while under a latter condition the stopping feature is absent and the only function of the worm is to turn the beam. When the motor is reversed the pawl l I i temporarily disconnects the friction mechanisms from the motor so that the latter need exert only enough energy to establish the desired maximum Warp tension.

Having thus described our invention it will be seen that changes and modifications may be made therein by those skilled in the art without departing from the spirit and scope of the invention and We do not wish to be limited to the details herein disclosed, but what we claim is:

1. In a loom having a warp beam supplying warp which passes over a whip roll and the tension oi which varies during loom operation, a normally idle electric motor, driving connections between the motor and the beam causing the latter to turn in a direction to reduce warp tension when the motor is running, a controller operatively related to part of the warp independently of the whip roll and responsive to changes in warp tension and having a contact which is closed when the warp tension reaches a given maximum, and electric means controlled by the contact causing the motor to run when said contact is closed.

2. In a 100m having a warp beam supplying warp which passes over a stationary whip roll and the tension of which varies during loom operation, an electric motor, driving connections between the motor and the beam effective when the motor is running to cause the beam to supply warp to reduce warp tension, a controller engaging part of the warp which passes over the whip roll and having a contact which is closed when the warp tension reaches a given maximum, and electric circuit means causing said motor to run when said contact is closed.

3. In a loom having a warpvbeam which turns to supply warp the tension oi' which varies during loom operation, a stationary whip roll over which the w'arp passes, a controller mounted stationarily with respect to the loom in front of the whip roll and having a contact which is closed when the warp tension reaches a given maximum, an electric motor operatively connected to the beam to cause turning thereof in a direction to reduce warp tension when the motor is running, and.

electric circuit means including the motor and contact eilective when said contact is closed to cause the motor to run.

4. In a loom having a warp beam which turns to supply warp the tension of which varies during loom operation, a. whip roll stationary with respeci*l to the loom and over which the warp passes when leading from the beam, part of the warp leading from the beam to one side of the whip roll and part of the warp leading forwardly from the other side of the Whip roll, an electric motor operatively connected to the beam and e'ective when running to turn the beam in sucl'ra direction as to reduce warp tension, a. controller engaging the warp at one side of the whip roll with respect to direction of travel of the warp there- 16 over and having a contact which is closed when the warp tension reaches a. given maximum. and electric circuit means eective to cause running of the motor when the contact is closed.

5. In a loom having a warp beam which turns to supply warp the tension of which varies during loom operation, the warp leading upwardly from the beam over a whip roll and then forwardly, a lnormally idle electric motor operatively connected to the beam and effective when running to cause the beam to turn in a direction to reduce warp tension, a controller engaging that part of the warp in front of the whip roll and having a contact which is closed when'the tension of the warp in front of the whip roll reaches a given maximum, -the tension in that part of the warp in front of the whip roll being due in part to frictional engagement of the warp with said whip roll, and electric circuit means causing the motor to run when said contact is closed.

6. In letoff mechanism for a loom having a warp beam provided with a gudgeon, a bearing on the loom for said gudgeon from which the gudgeon is removable by a rearward movement, a sprocket on said beam, an endless chain mounted for movement on the loom and meshing with said sprocket in frontV of said gudgeon only, and means permanently meshed with said chain to move the latter during loom operation in a direction to turn said beam to deliver warp.

7. In a letoff mechanism for a loom having a warp beam removable from the loom by a rearward motion, a chain sprocket on each end of the beam, a chain for each sprocket, guide means on the loom for each chain causingv the latter to mesh with the forward part only of the associated sprocket, and driving means eiective to move said chains in such a direction as to cause turning of both ends of the beam by said sprockets in a direction to deliver warp.

8. In a letoif mechanism for a loom having a warp beam removable from the loom by a rearward motion, a chain sprocket on each end oi the beam, a sprocket system for each end of the beam, each system including a pair of sprocket wheels, one above and the other below the corresponding sprocket, each system including a driving sprocket wheel, a chain for each system extending around the sprocket wheels thereof and meshing with the forward part of the corresponding sprocket intermediate the associated pair of sprocket wheels, a shaft for each driving sprocket in front of the beam, and power driven mechanism operatively connected to said shafts and eil'ective by power transmitted through said shafts and chains to turn both ends of the beam in a direction to deliver warp.

9. In a loom having a warp beam which turns to deliver warp the tensionof which varies dur- .ing loom operation, a controller responsive to variations in warp tension and having a contact which is closed when the warp tension attains a given maximum, a normally idle electric motor effectivewhen running to cause turning of the beam in a direction to reduce warp tension, electronic circuit means including the motor normally tending to cause the motor to run, grid circuit means controlled by said contact preventing the electronic circuit means from causing the motor to run when said contact is open but permitting said electronic circuit means to cause the motor to run when said contact is closed.

10. In a loom having a warp beam which turns to deliver warp the tension of which varies during loom operation, a contact which is closed when the warp tension attains a given maximum,

a normally idle electric motor effective when run-v ning to cause turning of the beam in a direction to reduce warp tension, an electronic tube having a grid, motor circuit means including the motor and tube normally tending to cause the motor to run and eiective to do so when cur-k rent can ilow through the tube, and grid circuit means under control of said contact normally effective when the latter is open to enable th grid to prevent iiow of current through the tube and thereby maintain the motor idle but effective when the contacty is closed to alter the electric condition of the grid to enable current to dow through the tube and eiiect running ci the motor.

11. In letoi mechanism for a loom having a warp beam operatively connected to an electric motor which when running turns the beam to de.. liver warp for the weaving'operation, a contact capable of assuming two conditions in one of which the contact is closed and in the other of which the contact is open, said contact being under control 0f the warp and being in onecondition when the tension of thegwarp is less than a desired maximum and being in the other condition thereof when the warp attains said desired maximum tension, motor operating electric circuit means including an electronic tube effective when current can now through the tube to cause the motor to run, a controlling grid for the tube, and grid circuit means controlled by said contact and eifective when the latter is in said one condition thereof to enable the grid to prevent flow of current through the tube and thereby prevent running of the motor and effective when said contact is in the other condition thereof to alter said grid and enable current to flow through said 1 tube, whereupon said electric circuit means causes running of the motor.

12. In letoif mechanism for a loom having a warp beam operatively connected .to an electric motor which when running turns the beam to deliver warp for the weaving operation, said motor being of the shunt wound type and having .an excited eld and an armature, armature controlling electric circuit means including an electronic tube and effective when electric current is able to pass through the tube to energize the armature and cause running of the motor, a control grid in said electronic tube, and grid circuit means controlled by the warp tension and effective when said tension is less than a desired maximum to enable the grid to prevent ilow of current in said armature controlling electric cir cuit means, said grid circuit means being effective when the warp tension attains said desired maximum to alter the electric condition of the grid in such manner as to permit passage of electric currentthrough the tube and enable said electric circuit means to energize the armature and cause running of said motor. l

13. In letoif mechanism for a loom having a warp beam operatively connected to an electric motor which when running turns the beam to deliver warp for the weaving operation, said motor being oi.' the direct current shunt wound type and having a eld coil which is constantly energized during `loom operation and having an armature independent of the field for intermittent energization, a transformer having a secondary provided with a center tap and constituting a source of alternating current, a pair of electronic gas containing tubes having plates one of which is connected to one end of said secondary and the other of which is connected to the other end 18 f o! the secondary so that said plates are alternately positive, electric circuit means including said tubes, secondary and motor and connected to said center tap and normally tending to cause running of the motor if electric current can pass through said tubes, a control grid for each tube, and grid controlling circuit means under control of the warp tension and effective when the warp tension is less than a desired maximum to enable the grids to prevent flow of current through their respective tubes and thereby prevent said electric circuit means from causing the motor to run, said grid controlling circuit means being effective when the warp tension attains said desired maximum to alter the electric condition of said grids to enable electric current to ilow through said tubes, whereupon said electric circuit means causes seid motor to run.

14. In letoff machanism for a loom having a warp beam operatively `connected to an electric motor which when running turns the beam to deliver warp for the weaving operation, electric circuit means for the motor under control of the warp and ineffective to cause running of the motor when the tension of the warp is less than a desired maximum but effective when the warp tension attains the desired maximum to cause said motor to run, and a manually controlled switch independent of the Warp and effective when closed during loom stoppage to cause said electric circuit means to effect running of the motor independently of the tension of the warp.

15. In ietoi mechanism for a loom having a warp beam operatively connected to an electric motor which when running turns the beam to deliverwarp for the weaving operation. e. contact which' is open when the tension o! the warp is less than a desired maximum but is closed when the warp tension attains the desired maximum. a manually operated switch independent of the warp tension, and electric circuit means effective during loom operation when said contact is closed to cause running of the motor, said contact when open during loom operation or loom stoppage normally preventing said electric circuit means from causing running of the motor, and electric connections between said switch and said electric circuit means eiective when the loom is stopped and said switch is closed to cause said -electric circuit means to effect running of the motor independently of said contact.

16. In a loom having a rotatably mounted warpv beam, an electric motor operatively connected to the' beam to cause rotation thereof, a contact responsive to variations in warp tension and closed when the tension is below a desired maxi- Y mum but open when the tension attains said desired maximum, a manually operated electric switch, and electric circuit means including the motor and controlled by said contact and switchl and effective when said contact and 4switch are closed to cause running of the motor ln a direction to cause the beam to wind warp thereon and increase warp tension to said desired maximum tension, whereupon said contact is opened and said motor stops running.

17. In a loom having a warp beam rotatable in a direction to tighten the warp, an electric motor operatively connected to the beamand eilective to rotate the beam in said direction, electronic circuit means for the motor, grid means controlling said electronic circuit means, grid controlling electric circuit means, a contact closed when the warp tension is less than a desired maximrum and open when the warp is at said desired maximum tension. and a normally open manually operated electric switch, said grid controlling circuit means including said contact and switch and effective when said contact and switch are closed to eiIect running of the motor by said electronic circuit means to cause the beam to increase warp tension to said desired maximum with resultant opening of said contact, said electronic circuit means being ineffective to cause further running of the motor after said contact is opened.

18. In a loom having a warp beam rotatable by an electric motor and in which the warp is slack and requires tightening to a desired maximum tension by reverse turning of the Warp beam by the motor, a contact responsive to changes in warp tension and closed when the warp tension is less than the desired maximum and open when the warp tension attains the desired maximum, a manual electric switch, and electric circuit means including the motor effective only when the contact and switch are closed to cause running of said motor to eiect reverse turning of the warp beam and thereby cause the warp to attain said desired maximum, whereupon said contact is open and said electric circuit means becomes ineffective to continue running of the motor.

19. In a loom having a warp beam rotatable in a forward direction' to deliver warp for the weaving process and rotatable in a reverse direction to tighten warp which is too slack for the weaving process, an electric motor operatively connected to the beam and eil'ective when running forwardly to cause forward rotation of the beam and effective when running backwardly to cause reverse rotation of the beam, electric circuit means eilective when closed to cause forward running of the motor, other electric circuit means effective when closed to cause backward running of the motor, and manual switch means controlling both oi.' said electric circuit means and movable to two diierent positions and effective when in one of said positions to cause the rst named electric circuit means to be closed and effective when in the other of said positions to cause said other electric circuit means to be closed.

20. In letoi mechanism for a loom having a lwarp beam operatively connected to an electric motor which when running turns the beam to deliver warp for the weaving operation, loom controlled electric switch means in one position when the loom is running and in another position when the loom is stopped, electric circuit means including said switch means eilective when the latter is in said one position only to cause running of the motor when the warp tension attains a desired maximum, and manually controlled electric circuit means including a manually operated switch and said loom controlled switch means and effective when the latter is in said other position only and the manually operated switch is closed to cause running of the motor.

21. In a loom having a warp beam rotatable in a forward direction to deliver warp for the weaving process and rotatable in a reverse direction to take up slackness of the warp, an electric motor operatively connected to the beam and effective when running forwardly to cause forward rotation of the beam and eflective when running backw-ardly to cause reverse rotation of the beam, electric circuit means effective when closed to cause the motor to run forwardly during loom operation when the warp tension attains a desired maximum, other electric circuit means effective when closed to cause the motor to run normally in neutral position but movable to either of two other positions, electric circuit means effective when said switch means is moved to one of said two positions to cause the motor to run forwardly, other electric circuit means eiIective when said switch means is moved to the other of said two positions to cause the motor to run backwardly, and means controlled by the loom by which each of said electric circuit means is dependent upon stoppage of the loom to effect running of the motor. l

23. In a loom having a warp beam rotatable in a forward direction to deliver warp for the weaving process, an electric motor operatively connected to the beam and effective when running to cause said beam to turn forwardly, a manually controlled switch, a loom controlled switch moving to a given position when the loom stops, and electric circuit means under the joint control of the manual switch and the loom controlled switch eilective only when the manual switch is closed and said loom control switch is in said given position thereof to eil'ect running of the motor to cause forward rotation of the beam.

24. In a loom having warp beam rotatable in a reverse direction to take up slackness in the warp, an electric motor operatively connected to the beam and eifective to cause reverse turning of the beam, loom control switch means which moves to a given position only when the loom is stopped, a normally open manually operated switch, and electric circuit means 'for the motor under the joint control of said switches and effective only when said loom control switch is in said given position thereof and the manual switch is closed to cause the motor to eil'ect reverse turning of the beam.

25. In leton mechanism for a loom having a warp beam operatively connected to an electric motor which when running turns the beam to deliver warp for the weaving operation, electronic electric circuit means including electronic tube means and eifective when current is able to now through said tube means to cause turning of the motor, grid means for the tube means, grid circuit means controlling the grid means and including a resistance, contact means for said grid control circuit means eilective when the tension of the warp is less than the desired maximum to enable said grid circuit means to create an electric condition at the grid means which prevents flow of current through the tube means, and a loom controlled switch effective when the loom is runcontact means from shortcircuiting said resistance.

2i 26. In letcff mechanism for a loom having warp beam operatively connected to an electric motor which when running turns the beam toA deliver warp for the weaving operation, electronic circuit means including electronic tube means effective when electricv current can pass through the tube means to cause running of the motor, grid means controlling the flow of electric 7current through said tube means, grid circuit means controlling the grid means and including a resistance, a contact under control of the warp and open when the warp tension is less than the desired maximum and closed when the warp tension attains said desired maximum, a loom controlled switch in one position when the loom is running and in another position when the loom is stopped, electric means connecting said contact and switch in a series circuit which is in parallel with said resistance' when said switch is inv said one position thereof,v said grid circuit means effective when the switch is in said one position thereof and said contact is open to enable the grid means to prevent flow of electric current through said tube means, said switch when in said one position thereof while said contact is closed shortcircuiting said resistance and causing said grid circuit means to effect a change in the grid means in such manner as to permit flow of electric current through the tube means, and said switch when in the other position thereof preventing said contact when closed from shorteircuiting said resistance.

27. In a loom having a warp beam rotatable forwardly to deliver warp for the weaving operation and rotatable reversely to take up warp when the latter is too slack for the weaving operation, an electric motor operatively connected to the beam causing forward rotation of the latter when the motor runs forwardly and causing reverse rotation of the beam when the motor runs backwardly, electronic tube means. grid means for the tube means controlling the flow of current through said tube means and normally preventing the flow of electric current through said tube means, a plurality of manual switches movable together and normally in a neutral position and movable from said neutral position to a forward position corresponding to forward running of the motor -and to a reverse position corresponding to backward running of the motor, grid control circuit means controlled by one of said manual switches and effective whether the latter be either in the forward position or the reverse position thereof to cause the grid means to permit electric current to flow through the tube means, electric circuit means including the tube means and closed through other of said manual switches when the latter are in the forward position thereof to effect forward running of the motor, and other electric circuit means including the tube means effective when said other manual switches are in thereverse position thereof to cause the motor to run backwardiy.

28. In a loom having a reciprocating lay which has a beatup motion each pick of the loom, the loom having a warp beam which turns to supply warp the tension of which varies during loom operation, an electric motor operatively connected the lay being greater than said given maximum. electronic tube means having control grid means, a motor circuit including the motor and tube means and effective when current can flow through the latter to cause running of the motor, a normally closed switch opened by the lay when the latter beats up, and grid circuit means including said contact and switch connected to the grid means and effective when said contact is open to maintain said grid in normal condition to prevent electric current from flowing through the tube means and effective only when the contact and switch are both closed to alter the grid and enable current to flow through the tube, said switch when open during closure of the contact causing said grid circuit means to maintain the grid in the normal condition thereof.

29. In a loom having av reciprocating lay which has a beatup motion each pick of the loom, the loom having a warp beam which turns to supply a warp the tension of which varies during loom operation. a contact which is closed when the warp tension attains a given maximum, the lay at each beatup causing the warp to attain a tension greater than said given'maximum, an electric switch normally closed but opened by the lay at each beatup thereof, an electric motor operatively connected to the beam and eective when running to turn the beam in a direction to reduce warp tension, electronic tube means having control grid means, motor circuit means including a motor and tube means and effective when current can flow through the tube to cause running of the motor. and grid circuit means including said contact and switch .in series and normally effective to enable thegrid means to prevent flow of current through the tube means when either the contact or the switch is open, said grid circuit means effective when the contact and switch are both closed to alter the condition of the grid means in such manner as to permit electric current to flow through the tube and cause running 0f the motor.

A30. In a loom having a warp beam which turns to supply warp the tension of which varies during loom operation. a takeup which exerts a given forward force on the warp tending to move the warp forwardly during loom operation, and two mechanisms acting jointly and each normally exerting rearward counter-forces on the warp which balance said given forward force and prevent forward movement of'the warp, one of said mechanisms providing a counter-force incapable -by itself of preventing the takeup from moving the warp forwardly, and the other of said mechanisms including an electric motor operatively connected to the beam and effective when the warp tension attains a given maximum to turn in a direction to reduce the counter-forcev exerted thereby sufficiently to enable the take-up to move the warp forwardly.

31. In a loom having a warp beam which turns to provide warp the tension of which varies during. loom operation. a takeup effective during loom operation to exert a given forward force on the warp tending to move the latter forwardly, friction means operatively connected to the beam and continuously exerting on the latter a counterforce less than said given force tending to resist turning of the beam and forward movement of the warp, and means supplementing the counter-force of said friction means by normally exerting an additional counter-force resisting turning of the beam in a direction to deliver warp forwardly when the warp tension is less than a given maximum but effective when the warp tension attains said given maximum to turn the warp beam in said direction and aid the takeup to move the warp forwardly.

32. In a loom having a warp beam which turns to supply warp the tension of which varies during loom operation, takeup mechanism exerting a given forward force on the warp during loom operation tending to move the warp forwardly, an electric motor, means operatively connecting the motor to the beam and effective when the motor is at rest to prevent turning of the warp beam, friction means operatively connected to the beam and normally exerting on said beam a rearward counter-force opposed to said given force and resisting turning of the beam, said motor when at rest and said friction means counter-balancing said given force of the takeup to prevent turning of the beam when the warp tension is less than a given maximum, and means effective when the warp tension attains said given maximum to cause turning of the motor to overcome the normal counter-force of the friction means and enable the takeup to move the warp forwardly.

33. In a loom operating with a warp beam supplying warp the tension of which varies during loom operation, the beam diminishing from a maximum diameter to a minimum diameter as a result of continued weaving by the loom, a takeup mechanism exerting-a given forward force on the warp and exerting a maximum turning torque on the beam when the beam diameter is maximum and exerting a minimum turning torque on the beam when the beam diameter is minimum, a motor operatively connected to the beam in such manner as to prevent beam rotation when the motor is at rest and cause beam rotation in a direction to deliverwarp forwardly when the motor is running, friction means exerting a given resistance to turning of the beam which can be overpowered by said maximum torque but not by said minimum torque, and means causing the motor to run when the warp tension attains a given maximum due to forward pull of the takeup on the warp, the motor when at rest aiding the friction means to resist the maximum torque of the takeup and the motor when running aiding the minimum torque of the-takeup to overcome said resistance of the friction means.

34. In a loom operating with a warp beam supplying warp the tension of which varies during loom operation, the beam diminishing from a maximum diameter to a minimum diameter as a result of continued weaving by the loom. a takeup mechanism exerting a given forward pull on the warp and exerting a maximum turning force on the beam when the beam diameter is maximum and exerting a minimum turning force on the beam when the beam diameter is minimum, a motor normally at rest but running when the warp tension attains a given maximum, driving connections between the motor and the beam, and friction means exerting a counterforce tending to prevent turning of the beam less than the maximum takeup turning force but greater than the minimum takeup turning force, said driving connections and friction means jointly resisting the takeup when the turning force of the latter is greater than the counterforce of the friction means and the motor is at rest, thereby enabling the takeup to develop said given maximum warp tension, and said driving connections and takeup jointly opposing the friction means counterforce when the latter is greater than the turning force of the takeup and the motor is running.

35. In a loom operating with a warp beam supplying warp the tension of which varies during loom operation, the beam diminishing from a maximum diameter to a minimum diameter as a result of continued weaving by the loom, a takeup mechanism exerting a given forward pull on the warp and exerting a maximum turning force on the beam when the beam diameter is maximum and exerting a minimum turning force on the beam when the beam diameter is minimum, a motor normally at rest but running when the warp tension attains a given maximum, driving connections between the beam and motor causing the beam to turn in a direction to deliver warp forwardly when the motor is running, said driving connections including a worm wheeloperatively connected to the beam and a worm for the worm wheel turning with the motor. stop means limiting longitudinal motion of the worm, and friction means exerting a resisting force tending to prevent turning of the beam, said resisting force being less than the maximum takeup turning force but greater than the minimum takeup turning force.

36. In a loom operating with a warp beam supplying warp the tension of which varies during loom operation, the beam diminishing from a maximum diameter to a minimum diameter as a result of continued weaving by the loom, the inertia of the beam diminishing as the diameter thereof diminishes. a takeup exerting a forward pull on the `warp and tending to overcome the inertia of the beam and turn the latter, the takeup and beam being capable of cooperating to create a tension in the warp above a desired maximum when the beam inertia is relatively large but being incapable of creating said desired maximum warp tension when the beam inertia is relatively small, friction means resisting rotation of the beam and capable of cooperating with the takeup and beam when the inertia of the latter is relatively small to create a warp tension above said desired maximum tension, motor means operatively connected to the beam effective when running to turn the beam against the resistance f of the friction means in a direction to reduce warp tension, and means effective to cause the motor to run when the 'warp tension reaches said desired maximum.

37. In a loom having a warp beam which rotates to deliver warp for the weaving process, an electric motor operative when running to supply power to turn the beam, a force transmitting member operatively connected to each end of the beam effective when moved to cause turning of the beam, differential mechanism operatively connected to the motor and said members and effective when thev motor is running to exert substantially equal forces on the ends of the beam tending to turn the latter, a friction mechanism operatively connected to each member, and means causing said friction members to exert substantially equal forces on their corresponding members tending to resist motion of the latter.

38. In a loom having a warp beam which turns to deliver warp for the weaving process, a shaft operatively connected to each end of the beam, a motor supplying power to turn the beam, differential mechanism operatively connecting the moltor to the shafts and effective to cause said shafts to exert substantially equal turning forces on both ends of the beam when the motor is running, a friction mechanism operatively connected 25 to each shaft tending to resist rotation thereof. and equalizing means for the friction mechanisms causing the latter to exert substantially equal forcesA on said shafts tending to resist turning thereof.

39. In a loom having a warp beam whichturns to deliver warp for the Weaving process, two axially aligned shafts one operatively connected to one end of the beam and the other operatively connected to the other end of the beam, said shafts when turning causing turning of the beam, a gear secured to each shaft, a motor supplying power to turn the beam, differential mechanism operatively connecting the motor to the gears ard effective to cause said shaftsto exert substantially equal turning forces on their corresponding ends of the warp beam, a friction mechanism operatively connected to each gear, and equalizing means for the. friction mechanism movably mounted on adjacent ends of said shafts and causing said mechanisms to exert substantially equal forces on their corresponding shafts tending to resist motion of the latter.

40. In a loom having a warp beam which turns to deliver warp for the weaving process, a shaft operatively connected to each end of the warp beam, said shafts effective when turning to cause turning of the beam, a gear turning with each shaft, a source of power to turn the beam, differential mechanism between said source and said gears effective to cause said shafts to exert sub-- stantially equal turning forces on the beam, a friction mechanism operatively connected to each gear, means limiting movement of one of said friction mechanisms in one direction axially of one of said shafts, the other friction mechanisms being mounted for axial movement along the other shaft, a member intermediate said friction rnechanisms operatively connecting the latter and causing the same to exert substantially equal forces on said shafts tending to resist turning of the latter, and mechanism urging said other frictionl mechanism and member toward said one friction mechanism.

41. In a loom having a. warp beam which turns to deliver Warp for the Weaving process, a source of power, a member operatively connected to each end of the warp beam, said members when moving effective to cause turning of the beam, differential mechanism operatively connecting said source'and said members causing a. driving force from said source to be divided substantially equally between said members to the end that the latter exerts substantially equal turning forces on the beam, and friction means operatively connected to said members and exerting substantially equal forces on the latter tending to resist movement thereof by said source.

42. In a loom having a warp beam which turns to deliver warp for the weaving process, a shaft operatively connected to each end of the warp beam, a source of power, differential mechanism operatively connecting said source to said shafts and effective to transmit substantially equal forcesfrom said source to said shafts to effect turning of the beam, a set of rotatable friction plates turning with each shaft, a member `intermediate said shafts, a second set of stationary friction disks for each shaft held against rotation by said member, and means including said of the beam, a friction mechanism operativelyl connected to each shaft, a stationary member intermediate said friction mechanisms, each friction mechanism having aset of friction disks moving with the corresponding shaft when the latter turns and engaging another set of friction disks held against movement by said member, said friction mechanisms exerting substantially equal forces on said shafts tending to resist turnmember forcing the rotatable ydislrs of each set into frictional relation with the corresponding set of stationary disks and causing said friction disks to exert substantially equal forces tending to re sist motion of said shafts.

ing thereof by power derived from said source and transmitted through said differential mechanism.

44. In a loom having a warp beam rotatable forwardly to reduce warp tension and rotatable backwardly to increase warp tension, a motor capable of runningA either forwardly or backwardly, driving connections between the motor and the beam turning the latter forwardly when the motor runs forwardly and turning the beam backwardly when the motor runs backwardly, friction means for the beam, and control means for the friction means effective to cause the latter to resist forward movement of the beam but causing the friction means to be ineffective to resist backward movement of the beam.

45; In a loom having a warp beam rotatable forwardly to reduce lwarp tension and rotatable reversely to increase warp tension, a motor operatively connected to the beam and effective when ruiming forwardly to effect forward turning of the beam and when running backwardly to effect reverse turning of the beam, friction mechanism, and control means for said friction mechanism causing the latter to be effective to resist forward movement of the warp beam but ineffective to resist reverse movement of the warp beam.

46. In a loom having a warp beam turning forwardly to reduce warp tension and turning reversely to increase warp tension, a motor operatively connected to the beam and effective when running forwardly to effect forward turning of the beam and effective when running backwardly to eect reverse turning of the beam, friction mechanism including parts operatively connected to the motor and moving when the latter runs and a member operatively connected to other parts of the friction mechanism frictionally engaging the first named parts, said member movingwith said other parts, and control means for said member effective when the motor is running forwardly to hold said member stationary to cause the friction mechanism to resist forward movement of the beam and operative when the motor is running backwardly to enable said member to move with said other parts and cause the friction mechanism to be Vineffective to resist reverse turning of the beam.

47. In a loom having .a warp beam rotatable forwardly 'to reduce warp tension and rotatable reversely to increase warp tension, an electric motor capable of running either forwardly or backwardly, and operating connections between each end of the beam and the motor, said connections effective to rotate the beam forwardly when the motor is running forwardly and rotate the beam reversely when the motor is running backwardly, a friction mechanism for each of said connections, and control means for said 27 friction mechanism causing the latter to resist forward rotation of the beam but ineffective io resist reverse rotation of the loom.

48. In a loom having a warp beam rotatable to supply a sheet of warp threads, rotary driving mechanism for each end of the beam. differential mechanism connected to each of said driving mechanisms, an electric motor eil'ective when running to cause said differential mechanism to e1'- fect rotation of both of said driving mechanisms to cause the latter to turn each end oi the beam at the same rate, contact means controlled by and responsive to variations in tension of a small group of warp threads of said sheet located between the sides of the latter, and electric circuit means controlled by said contact means and effective when the tension of said group of warp threads increases to a given value to cause nun' ning of the loom.

49. In a loom having a warp beam rotatable to supply a sheet of warp threads, an electric motor, contact means controlled by a small group of warp threads of said sheet between the sides of the latter responsive to variations in tension of the threads of said group, electric means controlled by the contact means and effective when the tension of the threads of said group attains a given maximum to cause the motor to run, and force transmitting means including a diierential mechanism operatively connecting the motor to each end of the beam and effective to cause turning of both ends of the beam at the same rate` and in a direction to deliver said sheet of warp when the motor runs.

50. In a loom having a warp-beam rotatable to supply a sheet of warp threads, a normally idle actuator, control means controlled by and il l) responsive to variations in tension of a small group of warp threads o! said sheet located be- REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 775,336 Meats Nov. 22, 1904 807,721I Carver Dec. 19, 1905 1,023,994 Coburn Apr. 23, 1912 1,548,993 Harris Aug. 11, 1925 1,703,884 Hutchins Mar. 5, 1929 1,749,131 Davis Mar. 4, 1930 1,817,203 Payne Aug. 4, 1931 2,143,200 Madden Jan. 10, 1939 2,169,326 Payne Aug. 15, 1939 2,227,355 Lawson Dec. 2l, 1940 2,340,889 Klumpp Eeb. 8, 1944 2,430,639 Jacques Nov. 11, 1947 FOREIGN PATENTS Number Country Date 409,724 Great Britain May 4, 1934 

